A pleated air filter should be replaced every 30-60 days, while a 2-fold air filter should be changed every 3 months. A 3-fold air filter should be changed every 120 days and a 4-fold air filter should be changed every 6 months. In general, most air filter manufacturers and HVAC companies recommend changing the air filter every 90 days or 3 months. This may vary depending on the location of your home, if you have pets, and the age of your system and equipment.
If you have pets in the house, it is recommended to change the filter every 60 days or 2 months. For households with multiple pets or people with allergies or respiratory conditions, it is best to change the filter every 20 to 45 days. Vacation homes or vacant homes that don't have much use can usually wait to change filters every 9-12 months. The more you use your home, the more often you need to change the air filter.
A general rule of thumb for pleated air filters (such as those manufactured by FilterBuy) is to replace the filter every 90 days. As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. If you wait too long to change the filter, indoor air quality will suffer. The longer the filter is in place, the more dirt, dust and allergens are trapped, clogging the filter and decreasing its efficiency.
Electrostatic filters can help you save money in the long run since they only need to be changed every 90 days. The Minimum Efficiency Report Value (MERV) scale provides professionals with a consistent standard to use when evaluating the quality of their air filters. Households with a pet should generally replace filters after two months; those with more than one pet may need to replace the filter once a month. If you have poor air quality outside or pets indoors, you'll need to replace your air filter more often.
If you don't want your air filter to blow more dirt into your home than there was before, it's highly recommended that you replace it every 30 days or within reason, as stated above.